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Biomedical subjects

J R Strub

Publications and source records attributed to J R Strub.

At least 19 recordsLinked to original sources
PubMed1995

Effects of Nd:YAG laser on wound healing processes: clinical and immunohistochemical findings in rat skin.

BACKGROUND AND OBJECTIVE: The clinical effects of the Nd:YAG laser in the rat skin as well as alterations of the extracellular matrix during healing were presented in this study. STUDY DESIGN/MATERIAL AND METHODS: This study evaluated the clinical effects of the Nd:YAG laser used with different energy parameters (low energy: 1.75 W and 20 pps/high energy: 3.0 W and 30 pps) in a duration 20-40 s in rat skin. Control incisions were performed with a scalpel blade. Rat skin incisions were examined over a period of 28 days by clinical photographs as well as by using immunohistochemical techniques in order to find the distribution and the amount of the extracellular matrix fibrillar components, i.e., collagen types I and III. RESULTS: Low energy laser treatment caused a rapid wound healing without scar tissue formation (compared to the high energy laser group) and clinical signs of scar tissue formation (compared to control incisions with the conventional scalpel). During the study period, the laser-induced lesions healed through reparative synthesis of the matrix proteins, which led to filling of the tissue defects. The regenerative processes were similar in the low-energy laser group and in the control incisions. In the high-energy lased tissues, we observed a delayed replacement of the defects by newly formed extracellular matrix proteins. CONCLUSIONS: This study showed a slower wound healing in the high-energy lased tissues. A similar healing in the low-energy lased tissues and in the incisions with the conventional scalpel was observed. The differences in the distribution of matrix proteins during healing and the coagulation of the tissues, which were exposed to low-energy laser treatment, might be the explanation for the minimal scarring, contraction, and pigmentation of the lased tissues as compared to conventional incisions.

Aluminum Silicates↗
PubMed1995

Influence of the suprastructure on the peri-implant tissues in beagle dogs.

The purpose of this study was to compare clinical, radiographic and histological differences around titanium oral implants loaded with either acrylic-veneered metal or ceramo-metal fixed prostheses. Five beagle dogs were used in this investigation. At the beginning of the study, all mandibular premolars and first molars were extracted. After 3 months of healing, 2 Brånemark implants were installed on each side of the mandibles. Three months later, abutments were inserted on each implant and a daily oral hygiene regime was initiated. One month after abutment connection, the implants on one side of the mandible were restored with an acrylic-veneered metal fixed prosthesis, whereas, on the other side a ceramo-metal fixed prosthesis was inserted. The prostheses were constructed in occlusion with the maxillary first molars. The following clinical parameters were measured around each implant at this time (i.e., baseline), and thereafter, at monthly intervals up to 5 months: Plaque Index; Gingival Index; implant mobility (using the Periotest); probing depth and clinical attachment level (using the Florida Probe). In addition, standardized radiographs were taken at baseline and 5 months after insertion of the prostheses and evaluated by subtraction radiography. Another Brånemark fixture was installed on each side of the mandibles 3 months before the end of the study. These implants remained unloaded and submerged for the entire study period. Five months after prosthesis insertion, the animals were killed, and implants with their supporting peri-implant tissues were processed for histological evaluation. Analyses of the clinical, radiographic and histometric parameters revealed no significant differences between the acrylic-veneered and ceramometal loaded implants.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗
PubMed1995

Treatment of exposed implant threads using a synthetic bone graft.

The aim of this study was to evaluate clinically and histologically the use of a synthetic bone graft (Ionogran) alone and in combination with guided bone regeneration (GBR) to facilitate bone regeneration and augmentation around exposed implant threads. Five male Beagle dogs were used in this investigation. Prior to the study all 3rd and 4th premolars were extracted. After 3 months, a flap was elevated and two Brånemark implants were inserted in each quadrant in such a way that two-three threads remained exposed over the alveolar bone. On the control sites the synthetic bone graft was then placed around the exposed threads and the flaps were repositioned and sutured. On the test sites, the same procedure was performed, but an expanded polytetrafluoroethylene barrier was placed to cover the bone graft and implants. Three months after implant placement, the barriers on the test sites were removed, healing abutments were inserted on all implants, and a thrice weekly plaque control regime was initiated. The following clinical parameters were measured at 1, 2, and 3 months: Plaque Index, Gingival Index, Probing Depth and Clinical Attachment Level. Three months after abutment connection the animals were killed and specimens were obtained for histological evaluation. Clinical parameters revealed a significant improvement on the experimental sites compared to control sites during the 3 month loading phase. Histological analyses, however, could not determine a difference in the nature of the implant/tissue interphase between experimental and control sites.

Aluminum Silicates↗
PubMed1995

[The recognition of mandibular asymmetries in the panoramic tomogram. An example of the need for judging the value of a diagnostic procedure].

According to Habets et al. (1988), dental rotational panoramic radiographs can be used to diagnose vertical asymmetries between the right (R) and left (L) mandibular condyle and/or ramus. The difference in vertical height between the two sides is expressed by an asymmetry index which is calculated with the formula (R - L)/(R + L) x 100%. The aim of this paper is to investigate the accuracy of this diagnostic method with the help of the parameters sensitivity and specificity. For each of 25 fully preserved and macerated skulls with a stable occlusion. Two dental rotational panoramic radiographs were made. The values obtained for condylar and rami heights as well as for the asymmetry indices as proposed by Habets and al. (1988) were compared with the values received from the corresponding measurements on the skulls. For the determination of sensitivity and specificity, the five highest asymmetry values found on the skulls were classified as "high asymmetry present". In order to achieve an acceptable sensitivity (.8), an insufficient specificity must be accepted (for ramus height .25, condyle height .2), resulting in a very high rate of false positive diagnoses. The study emphasizes the necessity of a critical evaluation of the utility of diagnostic tests and procedures.

Diagnostic Errors↗
PubMed1994

Influence of water storage and thermal cycling on the fracture strength of all-porcelain, resin-bonded fixed partial dentures.

The purpose of this in vitro study was to evaluate the influence of water storage and thermal cycling on the fracture strength of two designs of all-porcelain, resin-bonded fixed partial dentures made with the glass-infiltrated alumina ceramic In-Ceram. Forty frameworks of In-Ceram ceramic veneered with Vitadur-N porcelain were made to replace an upper central incisor bonded to extracted natural teeth. In 20 of the restorations the pontic was veneered only labially with Vitadur-N porcelain and no proximal box preparations were made (design A). The other 20 restorations had additional box preparations proximal to the pontic and the In-Ceram ceramic pontic framework was shifted to the labial aspect and veneered circumferentially with Vitadur-N porcelain (design B). Subgroups of 10 restorations were stored for 7 days in thymol solution or alternatively for 150 days in artificial saliva with thermal cycling for 18,750 cycles between 5 degrees and 55 degrees C. Restorations with design B had a statistically significantly higher fracture strength than restorations with design A. Storage in artificial saliva with thermal cycling significantly reduced the fracture strength of the resin-bonded In-Ceram fixed partial dentures. Therefore, the long-term clinical behavior of resin-bonded In-Ceram fixed partial dentures must be evaluated before general clinical use can be recommended.

Aluminum Oxide↗
PubMed1994

Titanium deposition in regional lymph nodes after insertion of titanium screw implants in maxillofacial region.

The deposition of titanium in regional lymph nodes was studied after insertion of endosseous, plasma-spray-coated titanium screw implants in a total of 19 beagle dogs. Five additional animals with no implants served as the control group. After killing the animals 9 months postoperatively, the regional lymph nodes were carefully excised, and samples were prepared for histologic examination. Other samples were used to identify foreign particles by energy-dispersive x-ray analysis and for measurement of the titanium concentration in the tissue by flameless atomic absorption spectroscopy. Very fine foreign-body particles could be seen in the histologic sections, and they were identified as titanium by energy-dispersive x-ray analysis. The atomic absorption analysis for titanium revealed a significantly higher concentration in the group with implants. The presence of very fine, poorly attached particles on the plasma-sprayed titanium surface suggests that these particles may be mechanically dislodged from the surface on insertion of the implants. This suggests that the fine particles may be transported by phagocytes to the regional lymph nodes, where they could be found without any signs of inflammation or foreign-body reaction.

Animals↗
PubMed1994

Bone augmentation using a synthetic bone graft in dogs.

The aim of this investigation was to evaluate clinically and histologically the use of a synthetic bone graft (Ionogran) alone and in combination with guided bone regeneration (GBR) for alveolar ridge augmentation. Five beagle dogs were used in this study. Prior to the augmentation procedure the maxillary and mandibular second, third and fourth premolars were extracted. Three months after the extractions, impressions from the area of the ridges were taken. Particles of Ionogran were then placed under mucoperiosteal flaps in each quadrant. On the experimental sites, an expanded polytetrafluoroethylene barrier was placed between the flap and the particles. Impressions were retaken at 1 and 3 months after surgery. Three months after surgery, the animals were sacrificed and specimens were prepared for histological evaluation. Computer-assisted volumetric analyses from the casts revealed an increase in ridge volume from baseline in both groups at 1 and 3 months. There was no difference in the height of the augmentation between the test and control sites. The histological results of this study indicate that this new synthetic bone graft appears to be a safe biocompatible grafting material. There were no apparent histological differences between the graft alone and graft/GBR sites. In both groups, however, graft particles were surrounded by dense fibrous connective tissue and bone formation was limited to the graft bone interface.

Aluminum Silicates↗
PubMed1992

[Severe atrophy of the alveolar ridge in edentulous patients. Combined treatment using bone grafts and screw implants].

In cases of advanced alveolar ridge atrophy, when the bone available for endosseous implants is not sufficient, endosseous implants are combined with augmentation of the alveolar ridge by means of autologous bone transplants. Depending on the type of atrophy found, the authors use three different surgical procedures: onlay technique, sandwich technique and alveolar extension technique. In all cases functional loading of the implants was performed by way of an entirely implant-supported bridgework. Results to date indicate that initial postoperative resorption is followed by a virtual standstill once the implants have been loaded.

Alveolar Process↗
PubMed1991

[Tensile strength of the bond to In-ceram after varying modes of surface conditioning].

The tensile bond strengths of six different resin-bonding-systems to the aluminium oxide ceramic In-Ceram were tested. The samples were stored in artificial saliva (37 degrees C) up to 150 days and thermocycled (5 degrees-55 degrees C, 18,750 cycles). After sandblasting or silicoating of In-Ceram the tensile bond strength of the modified Bis-GMA resin Panavia-Ex showed no significant changes within this observation period. Using the conventional Bis-GMA resin Microfill-pontic, silicoating In-Ceram with the Rocatec-system resulted in a better bond strength than the use of a silane. The used etching procedure with boiling 70% sulphuric acid was proven to be unsuitable for a long-term stable bond.

Acid Etching, Dental↗
PubMed1991

[Texture formation of the dental ceramic core material In-Ceram and thermal expansion of its individual components].

Electron microscopic investigations of the core material In-Ceram show how its texture is formed. While these are processed the Al2O3 crystallites turn idiomorphic. Etching the material with sulphuric acid selectively dissolves the glassy phase and reveals the crystallites. The chemical composition of the two components of the core material is determined by microprobe analysis. While the crystallites are pure Al2O3, the glass consists of La2O3, SiO2, Al2O3 and CaO. Measurements of the thermal expansions of the glass and the Al2O3 frame show the value for the glass to be 5.1% lower than that of the Al2O3 frame. This results in internal pressure and contributes to the high strength of the material.

Aluminum Oxide↗
PubMed1990

[Resin bonding bridges--state of the art].

Adhesive fixed partial denture (FPD) technology has gradually become viable in recent years, suitable for use in general dental practice. The most important prerequisites for success are patient selection and meticulous production techniques. Indications and limits of this technique are evaluated on the basis of the current state of the art. Initial preprosthetic treatment and clinical procedures are described. Research that has been done so far appears to demonstrate that adhesive FPDs are compatible with healthy periodontal tissues, even though some over-contouring of the adhesive tabs on the abutment teeth seems to be unavoidable. First clinical long-term studies have shown, however, that the failure rate of adhesive FPDs is higher than with conventional crown and bridge techniques. Porcelain-fused-to-metal FPDs on pure titanium frames and full ceramic FPDs are new developments in adhesive FPD technology which are not yet fit for use in dental practice.

Acid Etching, Dental↗